Flexible substrate

ABSTRACT

A flexible substrate includes a plurality of unit wiring structures. Each of the unit wiring structures includes: a central section; and at least four curved strips disposed at an outer side of the central section, each of the curved strips having a first end connected to the central section. The central section includes: an insulation layer; interlayer connection via that passes through the insulation layer; first wiring section connected to the interlayer connection via; and second wiring section electrically connected to the first wiring section by way of the interlayer connection via. The first wiring section, insulation layer and second wiring section are disposed in this order, and two of the at least four curved strips extending in a first direction are connected to the first wiring section, other two of the at least four curved strips extending in a second direction are connected to the second wiring section.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/730,855, filed on Jun. 4, 2015, claiming the benefit of priority ofJapanese Patent Application No. 2014-134415, filed on Jun. 30, 2014, theentire disclosures of which are all incorporated herein by reference.

BACKGROUND 1. Technical Field

The present disclosure relates to a flexible substrate.

2. Description of the Related Art

Flexible substrates have often been used in recent years together withthe miniaturization and thinning of electronic devices. The use offlexible substrates has been achieved in a variety of fields besides thefield of typical electronic devices. For example, the use of flexiblesubstrates has been achieved in wearable devices and the like besidesmobile devices such as smartphones.

Wearable devices are required to perform sensing close to the human bodyor to easily attach to movable parts or joints besides the wrist. Thedesign and the like are therefore considered important, with it beingimportant for the feeling experienced when a wearable device is worn tofit the movement of the user. Consequently, a flexible substrate isrequired to be provided with sufficient elasticity in addition toflexibility. A flexible substrate configured to be flexible and have anoverall serpentine form is known as a conventional technology (JapaneseUnexamined Utility Model Registration Application Publication No.1-135758, Japanese Unexamined Patent Application Publication No.2000-294886, Japanese Unexamined Patent Application Publication No.2004-71562, or Japanese Unexamined Patent Application Publication No.2004-349002).

SUMMARY

One non-limiting and exemplary embodiment provides a flexible substratethat is extensible.

In one general aspect, the techniques disclosed here feature a flexiblesubstrate including a plurality of unit wiring structures. Each of theplurality of unit wiring structures includes: a central section; and atleast four curved strips that are disposed at an outer side of thecentral section, each of the curved strips having a first end connectedto the central section. The central section includes: an insulationlayer; an interlayer connection via that passes through the insulationlayer; a first wiring section connected to the interlayer connectionvia; and a second wiring section electrically connected to the firstwiring section by way of the interlayer connection via. The first wiringsection, the insulation layer and the second wiring section are disposedin this order, and two of the at least four curved strips extending in afirst direction are connected to the first wiring section, other two ofthe at least four curved strips extending in a second direction areconnected to the second wiring section.

The flexible substrate of the present disclosure has sufficientelasticity.

Additional benefits and advantages of the disclosed embodiments willbecome apparent from the specification and drawings. The benefits and/oradvantages may be individually obtained by the various embodiments andfeatures of the specification and drawings, which need not all beprovided in order to obtain one or more of such benefits and/oradvantages.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view depicting a flexible substrateaccording to a first embodiment of the present disclosure;

FIG. 2 is a schematic perspective view depicting a unit wiring structurethat makes up the flexible substrate according to the first embodimentof the present disclosure;

FIG. 3 is a schematic perspective view depicting a state in which theflexible substrate according to the first embodiment of the presentdisclosure is extended;

FIG. 4 is a schematic perspective view depicting a state in which theflexible substrate according to the first embodiment of the presentdisclosure is made to adapt to the shape of a finger of a person;

FIG. 5 is a schematic plan view depicting a flexible substrate accordingto a second embodiment of the present disclosure and an electroniccircuit are electrically connected;

FIG. 6 is a schematic plan view of a flexible substrate according to athird embodiment of the present disclosure, in which each of the unitwiring structures has a single curved wiring section;

FIG. 7 is a schematic plan view depicting an example in which a flexiblesubstrate according to a fourth embodiment of the present disclosure isused as connection wiring;

FIGS. 8A to 8G show steps of a method for manufacturing the flexiblesubstrate of the first embodiment of the present disclosure;

FIGS. 9A to 9F show steps of a method for manufacturing the flexiblesubstrate of the second embodiment of the present disclosure;

FIG. 10 is a schematic diagram illustrating an idea at a preliminarystep that led to the conception of the flexible substrate of the presentdisclosure;

FIG. 11 is a schematic plan view depicting a flexible substrateaccording to a fifth embodiment of the present disclosure;

FIG. 12 is a schematic plan view depicting vertical curved wiringsections that make up unit wiring structures on which electronicelements are disposed;

FIG. 13 is a schematic plan view depicting an insulation sheet thatmakes up unit wiring structures on which electronic elements aredisposed;

FIG. 14 is a schematic plan view depicting horizontal curved wiringsections that make up unit wiring structures on which electronicelements are disposed;

FIG. 15 is a schematic plan view depicting electronic elements that makeup wiring structures on which electronic elements are disposed;

FIG. 16 is a schematic plan view depicting a flexible substrateaccording to a sixth embodiment of the present disclosure; and

FIG. 17 is a schematic plan view depicting a flexible substrateaccording to a seventh embodiment of the present disclosure.

DETAILED DESCRIPTION

First, an idea at a preliminary step that led to the present inventorconceiving of the flexible substrate according to an embodiment of thepresent disclosure will be described. The present inventor discovered aproblem in that it is possible for a conventional flexible substrate toextend and contract in the longitudinal direction of the flexiblesubstrate but it is difficult for a conventional flexible substrate toextend and contract in a direction that is different from this directionof extension, and despite having flexibility it is difficult to say thata conventional flexible substrate has sufficient elasticity of a degreethat responds to market needs. Furthermore, the present inventordiscovered a problem in that when a wiring section having a bent form isused, stress is likely to concentrate in the bent section duringextension and contraction. The present inverter carried out a diligentinvestigation in order to solve the aforementioned problems.

The present inventor developed a flexible substrate having a centralsection and one or a plurality of curved wiring sections (e.g. strips)that are disposed at the outer side of the central section and have oneend connected to the central section. The flexible substrate isextensible as a result of the curvature of each curved wiring sectionchanging during extension and contraction, and the flexible substratetherefore has sufficient elasticity.

Furthermore, in order to solve the problem of stress concentrating inpart of a wiring section and a breakage becoming likely to occur, thepresent inventor conceived of using a “curved” wiring section having arelatively large area such that stress is dispersed in the relativelylarge area, instead of a “bent” wiring section having a relatively smallarea. The area of the “curved” wiring section is 50% or more of that ofthe entire wiring section, for example. The area of the “bent” wiringsection is less than 50% of that of the entire wiring section, forexample. In other words, the present inventor thought that stress can bedispersed without being concentrated in one location by using a curvedwiring section that curves in the clockwise direction, for example,around the central section, as depicted in FIG. 10. It is therebypossible to reduce breakages of a flexible substrate even when theflexible substrate repeatedly extends and contracts. The presentinventor conceived of the flexible substrate according to an embodimentof the present disclosure on the basis of this idea.

Next, a flexible substrate according to an embodiment of the presentdisclosure will be described. The various kinds of elements depicted inthe drawings are merely illustrated in a schematic manner to aidunderstanding of the present disclosure, and the dimension ratios andthe appearance and the like can be different from the actual elements.

A flexible substrate according to an embodiment of the presentdisclosure is provided with two or more unit wiring structures. Eachunit wiring structure is provided with a central section and one or aplurality of strip-shaped curved wiring sections (strips, in otherwords) disposed at the outer side of the central section. Each curvedwiring section is disposed such that one end is connected to the outerperiphery of the central section belonging to the same unit wiringstructure and extends along the outer periphery, and the other end isconnected to a curved wiring portion of an adjacent unit wiringstructure, for example. In the present embodiment, it is sufficient forthe curved wiring section to have a wiring section that is at leastcurved; for example, a flexible substrate of a first embodiment depictedin FIG. 1 and the like is provided with a curved wiring section that iscurved approximately 180 degrees along the outer periphery of a centralsection 3, and a flexible substrate of a second embodiment depicted inFIG. 5 and the like is provided with a curved wiring section disposed soas to encircle the outer periphery of a central section.

In the present specification, with the center of a central section as areference point, the angle of a portion in which a curved wiring sectionis disposed curving along the outer periphery of the central section isreferred to as a curve central angle. However, this is anexemplification and, in the present disclosure, the curved wiringsection may be disposed curving approximately 30 degrees along the outerperiphery of the central section, for example, and may be disposedcurving approximately 90 degrees along the outer periphery of thecentral section. It is desirable that the curved wiring section becurved approximately 60 degrees or more along the outer periphery of thecentral section to increase the strip length of the curved wiringsections arranged between adjacent unit wiring structures. In addition,the curved wiring section may be disposed curving approximately 360degrees or more along the outer periphery of the central section. In thepresent specification, the case where the curved wiring section iscurved approximately 360 degrees or more along the outer periphery ofthe central section 3 refers to when the curved central section isdisposed wound around the outer periphery of the central section. In thecase where the curved wiring section is formed wound around the outerperiphery of the central section, it is desirable that the curved wiringsection be wound around the outer periphery of the central sectionapproximately one to three times. It should be noted that although theshape of the central section 3 is not particularly limited, it isdesirable that it be possible for a polygon shape such as aquadrilateral or a hexagon to be employed besides the aforementionedcircular shape, and that, in the case of a polygon shape, the apexesthereof be round-chamfered in accordance with the curve of the curvedwiring section.

Next, a flexible substrate 1 of the present disclosure when extendedwill be described. Here, a description will be given with reference toFIG. 3, which depicts a state in which the flexible substrate 1 of thefirst embodiment is extended. As depicted in FIG. 3, when the flexiblesubstrate 1 is extended, the curvature of a curved wiring section 4disposed along the outer periphery of the central section 3 changes suchthat the curvature decreases compared with before extension. The“curvature” mentioned in the present specification refers to the inverseof the radius of curvature. In other words, the curved wiring section 4deforms from one end of the curved wiring section 4 connected to thecentral section 3 toward the other end of the curved wiring section 4 insuch a way as to move away from the outer periphery of the centralsection 3, the curvature decreases, and the curved wiring section 4extends. Together with this, for example, in the flexible substrate 1 ofthe first embodiment, the center of the central section 3 of a unitwiring structure 2 and the center of the curved wiring section 4 of theunit wiring structure 2 become “deviated” from being substantially“aligned” prior to the extension, and the deviation between the centersincreases as the flexible substrate 1 is extended. However, the shape ofthe central section 3 of the unit wiring structure 2 does not deformduring the extension, as depicted in FIG. 3. In this way, the curvatureof the curved wiring section 4 disposed along the outer periphery of thecentral section 3 changes and allows the flexible substrate 1 of thepresent disclosure to extend and contract. Therefore extension andcontraction occur with the entirety of the curved wiring sectiondeforming, and stress can be dispersed across the entirety of the curvedwiring section. Consequently, in the flexible substrate 1 of the presentdisclosure, stress is unlikely to become concentrated and the occurrenceof a breakage can be suppressed.

Furthermore, in the flexible substrate of the present embodiment, forexample, it is possible for the length of the curved wiring section tobe increased by increasing the central angle at which curving isimplemented along the central section and increasing the number of timesthat winding is performed, and a greater elasticity can therefore bebrought about. To rephrase, it is possible for the initial substratedimensions before extension and contraction to be made smaller.

First Embodiment

Next, the flexible substrate 1 of the first embodiment of the presentdisclosure will be described.

The flexible substrate 1 of the first embodiment of the presentdisclosure is provided with a plurality of unit wiring structures 2arranged in a matrix form as depicted in FIG. 1. In the flexiblesubstrate 1 of the first embodiment of the present disclosure, each unitwiring structure 2 is provided with four curved wiring sections 4arranged at equal intervals at the outer periphery of a circular centralsection 3, as depicted in FIG. 2. These curved wiring sections 4 arearranged in a symmetrical manner with respect to the center of thecentral section 3. Specifically, the four curved wiring sections 4 arearranged at equal intervals at the outer periphery of the centralsection 3. When the four curved wiring sections 4 are arranged at equalintervals at the outer periphery of the central section 3, there are twolines that correspond to the diameter of the central section 3 and jointhe ends of mutually opposing curved wiring sections 4, and the twolines are orthogonal.

The unit wiring structures 2 can be disposed side-by-side in onedirection, and the unit wiring structures 2 can also be disposed in adirection orthogonal to the one direction. In other words, it ispossible for adjacent unit wiring structures 2 to be disposed in thevertical and horizontal directions. Consequently, it becomes possiblefor the unit wiring structures 2 to be arranged in a matrix form asdepicted in FIG. 1. For that reason, the flexible substrate 1 of thefirst embodiment of the present disclosure can be made to extend andcontract not only in one direction but also in an orthogonal directionthat is different from the one direction. Consequently, the flexiblesubstrate 1 of the first embodiment of the present disclosure eliminatesthe problem of the conventional flexible substrate which can extend andcontract in the longitudinal direction, but have difficulties to extendand contract in other directions. Consequently, the flexible substrate 1of the first embodiment of the present disclosure can adapt to complexshapes such as a finger of a person as depicted in FIG. 4. Specifically,it is possible for the flexible substrate 1 to be applied also towearable devices that are required to perform sensing close to a humanbody or to easily attach to movable parts or joints besides the wrist.

Second Embodiment

Next, a flexible substrate 10 of a second embodiment of the presentdisclosure will be described.

The flexible substrate 10 of the second embodiment of the presentdisclosure is provided with a first unit wiring structure 21, a secondunit wiring structure 22, and a third unit wiring structure 23 disposedside-by-side in one direction as depicted in FIG. 5. In the flexiblesubstrate 10 of the second embodiment of the present disclosure, each ofthe first unit wiring structure 21, the second unit wiring structure 22,and the third unit wiring structure 23 is provided with a centralsection 30 and two curved wiring sections 40. Each of the two curvedwiring sections 40 has one end connected to a central section 30 and isdisposed along the outer periphery of the central section 30. When theflexible substrate 10 of the second embodiment of the present disclosureis extended, the curvature of the curved wiring sections 40 disposedalong the outer periphery of the central section 30 changes such thatthe curvature decreases compared with before extension. Together withthis, each curved wiring section 40 extends from one end of the curvedwiring section 40 connected to the central section 30 toward the otherend of the curved wiring section 40 in such a way as to move away fromthe outer periphery of the central section 30. However, the shapes ofthe central sections 30 of the first unit wiring structure 21, thesecond unit wiring structure 22, and the third unit wiring structure 23do not deform during the extension. Consequently, it becomes possiblefor the flexible substrate 10 of the second embodiment of the presentdisclosure to be extended and contracted as a result of only thecurvature of the curved wiring sections 40 disposed along the outerperiphery of the central sections 30 changing.

Furthermore, in the first unit wiring structure 21 and the second unitwiring structure 22, one curved wiring section 40 of the first unitwiring structure 21 and one curved wiring section 40 of the second unitwiring structure 22 are connected. Electronic elements 6 are disposed onthe central sections 30 connected to the one ends of the curved wiringsections 40. Furthermore, in the first unit wiring structure 21, one endof the other curved wiring section 40 is electrically connected to anelectronic circuit 5. In the second unit wiring structure 22 and thethird unit wiring structure 23, the other curved wiring section 40 ofthe second unit wiring structure 22 and one curved wiring section 40 ofthe third unit wiring structure 23 are connected. Furthermore, in thethird unit wiring structure 23, one end of the other curved wiringsection 40 is electrically connected to an electronic circuit. Theelectronic circuit 5 and the electronic elements 6 can thereby beelectrically connected by way of the highly elastic flexible substrate10 of the present disclosure, as depicted in FIG. 5. Consequently, it ispossible to provide a wearable device or the like that is able to beattached to a site of the human body that extends and contracts to agreat extent.

Third Embodiment

Next, a flexible substrate 100′ of a third embodiment of the presentdisclosure will be described.

FIG. 6 is a schematic plan view of the flexible substrate 100′ of thethird embodiment of the present disclosure. In the flexible substrate100′, curved wiring sections 400′ of unit wiring structures 200′ aremade up of one curved wiring section. Two unit wiring structures 200′are disposed side-by-side in one direction. One of the unit wiringstructures 200′ is provided with a central section 300′ in which anelectronic element 6 is disposed as depicted in FIG. 6, and one curvedwiring section 400′ disposed at the outer periphery of the centralsection 300′. The curved wiring section 400′ has one end connected tothe central section 300′ and is disposed along the outer periphery ofthe central section 300′. Furthermore, the other unit wiring structure200′ is provided with a central section 300′ in which a processingcircuit 7 is disposed as depicted in FIG. 6, and one curved wiringsection 400′ disposed at the outer periphery of the central section300′. The curved wiring section 400′ has one end connected to thecentral section 300′ and is disposed along the outer periphery of thecentral section 300′. Furthermore, the other end of the curved wiringsection 400′ of the one adjoining unit wiring structure 200′ and theother end of the curved wiring section 400′ of the other unit wiringstructure 200′ are connected.

In the flexible substrate 100′ of the third embodiment of the presentdisclosure, for example, when a sensor element is disposed as theelectronic element 6 on the central section 300′ of the one unit wiringstructure 200′ and the processing circuit 7 is disposed on the centralsection 300′ of the other unit wiring structure 200′, overall it ispossible for an attachable sensing system to be provided on a site ofthe human body that extends and contracts to a great extent.

It should be noted that, in the aforementioned first to thirdembodiments, an insulation sheet and wiring disposed on both mainsurfaces of the insulation sheet are provided together with the centralsections and the curved wiring sections. In this case, the wiringdisposed on both main surfaces of the insulation sheet is electricallyconnected by way of interlayer connection vias. (In contrast to this, afourth embodiment described later includes a cross-sectional structureformed mainly from wiring, as well as the central sections and thecurved wiring sections.) Furthermore, in the third embodiment, a unitwiring structure may be provided with three curved wiring sections atthe outer periphery of a central section, and these curved wiringsections may be arranged in a symmetrical manner with respect to thecenter of the central section. In other words, it is possible for threeadjacent unit wiring structures to be arranged so as to be positioned atthe apexes of a triangle. In this case, a unit wiring structure isadditionally arranged in an adjacent manner in another direction thatintersects the one direction in which two adjacent unit wiringstructures are arranged side-by-side, and curved wiring sections aremutually connected between adjacent unit wiring structures.

Fourth Embodiment

Next, a flexible substrate 100 of a fourth embodiment of the presentdisclosure will be described.

FIG. 7 is a schematic plan view depicting an example in which theflexible substrate 100 of the fourth embodiment of the presentdisclosure is used as connection wiring. As depicted in FIG. 7, at leasttwo electronic elements 6, sensor elements for example, are electricallyconnected by way of the flexible substrate 100 of the fourth embodimentof the present disclosure. The flexible substrate 100 of the fourthembodiment of the present disclosure is made up of wiring without usingan insulation sheet. That is, the flexible substrate 100 of the fourthembodiment of the present disclosure functions as connection wiring. Theflexible substrate 100 of the fourth embodiment of the presentdisclosure is provided with a central section 300 and two curved wiringsections 400. Each of the two curved wiring sections 400 has one endconnected to the central section 300 and is disposed along the outerperiphery of the central section 300. When the flexible substrate 100 ofthe fourth embodiment of the present disclosure is to function asconnection wiring, the central section 300 does not require a space forproviding an electronic element. Therefore, the central section 300 doesnot have to be circular and may be S-shaped as depicted in FIG. 7, forexample. Furthermore, because the flexible substrate 100 of the fourthembodiment of the present disclosure is able to function as connectionwiring, the central section 300 and also the curved wiring sections 400may be structures provided with only wiring without having an insulationsheet.

It is possible for the flexible substrate 100 of the fourth embodimentof the present disclosure to be used between sensor groups that monitorthe state of a human body and between processing circuits and the like,for example. It is thereby possible to provide a sensing system that isable to be attached to a site of the human body that extends andcontracts to a great extent.

Fifth Embodiment

Next, a flexible substrate 1′ of a fifth embodiment of the presentdisclosure will be described.

FIG. 11 is a schematic plan view depicting the flexible substrate 1′according to the fifth embodiment of the present disclosure. Theflexible substrate 1′ of the fifth embodiment of the present disclosureis provided with a plurality of unit wiring structures arranged in amatrix form similar to the flexible substrate 1 of the first embodimentof the present disclosure. The unit wiring structures are provided witha plurality of curved wiring sections 4′ arranged at equal intervals atthe outer periphery of a circular central section. The plurality ofcurved wiring sections 4′ are arranged in a symmetrical manner withrespect to the center of the central section. In the fifth embodiment,as depicted in FIG. 11, electronic elements 6 (LED elements, forexample), row driver elements 24 for driving the electronic elements 6arranged in the row direction, column driver elements 25 for driving theelectronic elements 6 arranged in the column direction, and a controlelement 26 electrically connected to the row driver elements 24 and thecolumn driver elements 25 are disposed on the plurality of unit wiringstructures arranged in a matrix form.

Specifically, in the fifth embodiment, as depicted in FIG. 11, theelectronic elements 6 disposed on the unit wiring structures arearranged in a matrix form. The unit wiring structures on which theseelectronic elements 6 are disposed form a structure in which verticalcurved wiring sections 4′ (see FIG. 12), an insulation sheet 27 (seeFIG. 13), horizontal curved wiring sections 4′ (see FIG. 14), and theelectronic elements 6 (see FIG. 15) are disposed from below in thisorder. The vertical curved wiring sections 4′ and the horizontal curvedwiring sections 4′ are electrically connected by way of interlayerconnection vias 12 that pass through the insulation sheet 27. In thefifth embodiment, from among the unit wiring structures on which theelectronic elements 6 are disposed, the unit wiring structures providedwith the electronic elements 6 that are disposed side-by-side in anoutermost column are electrically connected by way of the curved wiringsections 4′ to the respective unit wiring structures provided with therow driver elements 24. In other words, the unit wiring structuresprovided with the row driver elements 24 are disposed so as to bearranged opposing the unit wiring structures provided with theelectronic elements 6 that are disposed side-by-side in the outermostcolumn. Adjacent row driver elements 24 disposed on the unit wiringstructures are electrically connected to each other by way of the curvedwiring sections 4′.

Here, it is desirable that from among the curved wiring sections 4′, thecurved wiring sections 4′ that electrically connect adjacent row driverelements 24 be made thicker than other curved wiring sections 4′ (inother words, the curved wiring sections 4′ for electrically connectingthe electronic elements 6). It is because the curved wiring sections 4′that electrically connect adjacent row driver elements 24 are impactedfrom the outside and are caused to electrically conduct more often thanthe other curved wiring sections 4′. Furthermore, from among the unitwiring structures on which the electronic elements 6 are disposed, theunit wiring structures provided with the electronic elements 6 that aredisposed side-by-side in an outermost row are electrically connected byway of the curved wiring sections 4′ to the respective unit wiringstructures provided with the column driver elements 25. In other words,the unit wiring structures provided with the column driver elements 25are disposed so as to be arranged opposing the unit wiring structures 2′provided with the electronic elements 6 that are disposed side-by-sidein the outermost row. Adjacent column driver elements 25 disposed on theunit wiring structures are electrically connected each other by way ofthe curved wiring sections 4′. Here, it is desirable that from among thecurved wiring sections 4′, the curved wiring sections 4′ thatelectrically connect adjacent column driver elements 25 be made thickerthan other curved wiring sections 4′ (in other words, the curved wiringsections 4′ for electrically connecting the electronic elements 6). Itis because the curved wiring sections 4′ that electrically connectadjacent column driver elements 24 are impacted from the outside and arecaused to electrically conduct more often than the other curved wiringsections 4′.

A method for driving the electronic elements 6 is as follows. First,control data is sent from the control element 26 (specifically, from amicrocomputer via the control element 26) to each column driver element25 by way of the curved wiring sections 4′, and current that flows ineach column direction is controlled in accordance with the control data.Furthermore, control data is sent from the control element 26 to eachrow driver element 24 by way of the curved wiring sections 4′, andcurrent that flows in each row direction is controlled in accordancewith the control data. In respective column driver elements 25,sequential data transfer units such as shift registers may be mounted.In this case, the control element 26 may send a control signal to turnon the column driver elements 25, and the sequential data transfer unitsmay sequentially transfer the signal to the column driver elements 25.Thereby, each column can be turned on in sequence. Furthermore, inrespective row driver elements 24, sequential data transfer units suchas shift registers may be mounted. In this case, the control element 26may send a control signal to turn on the row driver elements 24, and thesequential data transfer units may sequentially transfer the signal tothe row driver elements 24. Thereby, each row can be turned on insequence. Thus, by using the combination of the row driver elements 24and the column driver elements 25, the luminance of an electronicelement 6 (an LED element, for example) in a prescribed location can becontrolled for display. Consequently, in the fifth embodiment, LEDelements in which RGB tri-color elements, for example, are mounted canbe used to control a full-color display.

In the fifth embodiment, the electronic elements 6, the row driverelements 24, the column driver elements 25, and the control element 26are disposed on the unit wiring structures that are provided with theplurality of curved wiring sections 4′ arranged at equal intervals atthe outer periphery of circular central sections as described above.Thus, the concentration of stress and the occurrence of breakages can besuppressed and the elasticity of the flexible substrate 1′ can beensured. Moreover, it is also possible to cause a desired electronicelement 6 to be driven.

In the first to fifth embodiments, one end of a curved wiring section ofa unit wiring structure is connected to a central section whereas theother end of the curved wiring section of the unit wiring structure isconnected to a curved wiring unit of an adjacent unit wiring structure.The connection point where the other end of a curved wiring section ofone unit wiring structure and the other end of a curved wiring sectionof another unit wiring structure are connected is an “inflection point”.An inflection point is a point where concavity and convexity change on acurve, in other words, a point where a curve switches from being convexfrom below to being convex from above, or a point where a curve switchesfrom being convex from above to being convex from below. However, in theflexible substrate of the present disclosure, a connection point wherethe other end of a curved wiring section of one unit wiring structureand the other end of a curved wiring section of another unit wiringstructure are connected does not necessarily have to be an “inflectionpoint”. For example, it is possible for the following aspect to also beadopted.

Sixth Embodiment

Next, a flexible substrate 10′ of a sixth embodiment of the presentdisclosure will be described.

FIG. 16 is a schematic plan view depicting the flexible substrate 10′according to the sixth embodiment of the present disclosure. Theflexible substrate 10′ of the sixth embodiment of the present disclosureis provided with a plurality of unit wiring structures 20′ arranged in amatrix form as depicted in FIG. 16. The flexible substrate 10′ of thesixth embodiment of the present disclosure is different from the firstto fifth embodiments in not having inflection points at connectionpoints where the other end of a curved wiring section 40′ of one unitwiring structure 20′ and the other end of a curved wiring section 40′ ofanother unit wiring structure 20′ are connected. In the flexiblesubstrate 10′ of the sixth embodiment of the present disclosure, a unitwiring structure 20′ is provided with four curved wiring sections 40′arranged at equal intervals at the outer periphery of a circular centralsection 30′, as depicted in FIG. 16. These curved wiring sections 40′are arranged in a symmetrical manner with respect to the center of thecentral section 30′.

Seventh Embodiment

Next, a flexible substrate 10″ of a seventh embodiment of the presentdisclosure will be described.

FIG. 17 is a schematic plan view depicting the flexible substrate 10″according to the seventh embodiment of the present disclosure. Theflexible substrate 10″ of the seventh embodiment of the presentdisclosure is similar to the sixth embodiment and different from thefirst to fifth embodiments in not having inflection points at connectionpoints where the other end of a curved wiring section 40″ of one unitwiring structure 20″ and the other end of a curved wiring section 40″ ofanother unit wiring structure 20″ are connected. The flexible substrate10″ according to the seventh embodiment of the present disclosure isprovided with a plurality of unit wiring structures 20″. The unit wiringstructures 20″ are provided with four curved wiring sections 40″arranged at equal intervals at the outer periphery of a circular centralsection 30″ as depicted in FIG. 17. These curved wiring sections 40″ arearranged in a symmetrical manner with respect to the center of thecentral section 30″.

In the sixth and seventh embodiments, as in the first to fifthembodiments, when the flexible substrate is extended, the curvatures ofthe curved wiring sections disposed along the outer periphery of thecentral section change such that the curvatures decrease compared withbefore extension. However, the shapes of the central sections of theunit wiring structures do not deform during the extension. In this way,in the flexible substrates of the sixth and seventh embodiments of thepresent disclosure, the curvatures of the curved wiring sectionsdisposed along the outer periphery of the central sections change andallow the flexible substrates to extend and contract, and thereforeextension and contraction occurs with the entirety of the curved wiringsections deforming, and stress can be dispersed across the entirety ofthe curved wiring sections. Consequently, stress is unlikely to becomeconcentrated and the occurrence of a breakage can be suppressed also inthe flexible substrates of the sixth and seventh embodiments of thepresent disclosure.

Here, the materials of the insulation sheet and wiring used in theaforementioned embodiments will be discussed. It is desirable that theinsulation sheet be formed from at least one kind of material selectedfrom the group consisting of polyethylene terephthalate (PET),polyethylene naphthalate (PEN), polyether ether ketone (PEEK), polyimide(PI), and a liquid crystal polymer and the like, for example. The wiringis not particularly limited as long as the wiring exhibits conductivity.Possible examples of materials for a conductor layer used in theaforementioned embodiments are a metal material such as gold (Au),silver (Ag), copper (Cu), nickel (Ni), chromium (Cr), cobalt (Co),magnesium (Mg), calcium (Ca), platinum (Pt), molybdenum (Mo), iron (Fe)and/or zinc (Zn), or a conductive oxide material such as zinc oxide(ZnO), tin oxide (SnO₂), indium tin oxide (ITO), fluorine-containing tinoxide (FTO), ruthenium oxide (RuO₂), iridium oxide (IrO₂) and/orplatinum oxide (PtO₂), and, in addition, a conductive polymer materialsuch as a polythiophene-based and/or a polyaniline-based material. Itshould be noted that when the wiring is disposed on insulation sheet,coating processing or sealing processing may be carried out with aninsulative material.

Furthermore, the “electronic element” is not particularly limited andpossible examples include a semiconductor element, a temperature sensor,a pressure sensor, and an actuator and the like. A semiconductor elementmentioned here essentially refers to a light emitting element, a lightreceiving element, a diode, and a transistor and the like. Otherspecific examples of an electronic element that can be given include anIC (a control IC, for example), an inductor, a capacitor, a powerelement, a chip resistance, a chip capacitor, a chip varistor, a chipthermistor, another chip-shaped laminated filter, and a connectionterminal and the like.

[Method for Manufacturing Flexible Substrate of the Present Disclosure]

Next, a method for manufacturing a flexible substrate according to anembodiment of the present disclosure will be described.

First Embodiment (Aspect in which Wiring is Disposed on Both MainSurfaces of Insulative Sheet)

(Preparation of Insulation Sheet+Forming Metal Foil on Insulation Sheet)

First, as depicted in FIG. 8A, an insulation sheet 8 is prepared and ametal foil 13 (thickness 5 to 50 μm) is formed on both main surfaces ofthe insulation sheet 8. At least one from the group consisting ofpolyethylene terephthalate (PET), polyethylene naphthalate (PEN),polyether ether ketone (PEEK), polyimide (PI), and a liquid crystalpolymer and the like can be selected as the insulation sheet 8. In thepresent embodiment, it is desirable that an insulation sheet 8 formedfrom polyimide that has flexibility/bendability be used. The metal foil13 is not particularly limited to a particular material and a copperfoil can be used, for example.

It should be noted that although the metal foil 13 is formed on bothmain surfaces of the insulation sheet 8 in the present embodiment, thepresent disclosure is not limited thereto and the metal foil 13 may beformed on one main surface of the insulation sheet 8.

(Pattern Forming)

Next, as depicted in FIG. 8B, desired locations of the metal foil 13formed on both main surfaces of the insulation sheet 8 are etched toform prescribed wiring patterns 11. Specifically, wiring patterns 11made up of central section precursors 19 and curved wiring sectionprecursors 18 that have one end connected to a central section precursor19 and are disposed along the outer periphery of a central sectionprecursor 19 are formed.

(Forming Interlayer Connection Vias)

Next, through holes that pass from the wiring patterns 11 formed on onemain surface of the insulation sheet 8, through the insulation sheet 8,to the wiring patterns 11 formed on the other main surface of theinsulation sheet 8 are formed in regions in which electronic elements 6and the like described hereinafter are to be placed. Next, as depictedin FIG. 8C, plating processing, for example, is carried out on thethrough holes to form interlayer connection vias 12.

(Forming Wiring Protection Sheets)

Next, as depicted in FIG. 8D, wiring protection sheets 15 are disposedso as to cover the wiring patterns 11 except in regions in which theelectronic elements 6 and the like described hereinafter are to beplaced.

(Placing Electronic Elements)

Next, as depicted in FIG. 8E, the electronic elements 6 are disposed onthe exposed wiring patterns 11.

(Laser Cutting)

Next, as depicted in FIG. 8F, prescribed locations of the wiringprotection sheet 15 and the insulation sheet 8 are cut away by lasercutting. The prescribed locations of the wiring protection sheet 15 andthe insulation sheet 8 are between the wiring patterns 11 when viewedfrom a direction perpendicular to the main surface of the insulationsheet 8. Central sections 3 and curved wiring sections 4 that have oneend connected to a central section 3 and are disposed along the outerperiphery of a central section 3 are thereby formed. According to theabove, the flexible substrate 1 of the present disclosure can be formed.As depicted in FIG. 8F, each curved wiring section (a strip, in otherwords) 4 has a gap between a side surface thereof and a side surface ofa central section 3, and between a side surface thereof and a sidesurface of another curved wiring section 4. As a result of having thesegaps, the degree of freedom for the change in curvature of each curvedwiring section increases, and the flexible substrate 1 is extensible inthe planar direction and perpendicular direction thereof.

(Coating Flexible Member)

In addition, as depicted in FIG. 8G, the entirety of the flexiblesubstrate of the present disclosure may be covered by a flexible member16 such as an elastomer.

It should be noted that, in order to ensure the elasticity of theflexible substrate 1 of the present disclosure, it is desirable that thethickness of the flexible member 16 such as an elastomer that isdisposed in gap portions between the curved wiring sections 4 be lessthan the thickness of the flexible member 16 such as an elastomer thatis disposed on the curved wiring sections 4. It should be noted that aprecursor solution for the flexible member 16 may be spray coated on theflexible substrate 1 of the present disclosure. Furthermore, theconcentration of a precursor solution for the flexible member 16 that itis applied in the gap portions between the curved wiring sections 4 andthe concentration of a precursor solution for the flexible member 16that is applied on the curved wiring sections 4 may be adjusted inadvance, and then the precursor solutions may be applied to the gapportions and the curved wiring sections 4.

Second Embodiment (Aspect in which Wiring is Disposed on One MainSurface of an Insulation Sheet)

(Forming of Metal Foil)

First, as depicted in FIG. 9A, a metal foil 130 is affixed to one mainsurface of a temporarily fixed sheet 14 (thickness 5 to 50 μm). Themetal foil 130 is not particularly limited to a particular material anda copper foil can be used, for example.

(Pattern Forming)

Next, as depicted in FIG. 9B, desired locations of the metal foil 130affixed to the one main surface of the temporarily fixed sheet 14 areetched to form prescribed wiring patterns 110. Specifically, wiringpatterns 110 made up of central section precursors 190 and curved wiringsection precursors 180 that have one end connected to a central sectionprecursor 190 and are disposed along the outer periphery of a centralsection precursor 190 are formed.

(Placing Electronic Elements)

Next, as depicted in FIG. 9C, electronic elements 6 are disposed on thewiring patterns 110. In this case, the electronic elements 6 aredisposed in portions corresponding to central sections of the flexiblesubstrate of the present disclosure that will be ultimately obtained.

(Coating Flexible Member)

Next, as depicted in FIG. 9D, the wiring patterns 110 and the electronicelements 6 disposed on the wiring patterns 110 are covered with aflexible member 160 such as an elastomer.

(Detaching Temporarily Fixed Sheet)

Next, as depicted in FIG. 9E, the temporarily fixed sheet 14 isdetached. At such time, the wiring patterns 110 are exposed due to thetemporarily fixed sheet 14 being detached.

(Coating Flexible Member)

Next, as depicted in FIG. 9F, the exposed wiring patterns 110 arecovered with a flexible member 160′ such as an elastomer. This flexiblemember 160′ functions as an insulation sheet.

According to the above, the flexible substrate of the present disclosurecan be formed.

Heretofore, the flexible substrate of the present disclosure has beendescribed; however, the present disclosure is not limited thereto, andit is to be understood that various alterations may be implemented by aperson skilled in the art without deviating from the scope of thepresent disclosure defined by the scope of the patent claimshereinafter.

A flexible substrate according to an embodiment of the presentdisclosure comprises a plurality of unit wiring structures. Each of theplurality of unit wiring structures comprises a central section and oneor a plurality of strips disposed at an outer side of the centralsection. Each of the one or plurality of strips has a first end and asecond end, is curved, and includes wiring. The first end is connectedto the central section. The plurality of unit wiring structures includea first unit wiring structure and a second unit wiring structure thatare mutually adjacent. The second end of at least one of the one orplurality of strips of the first unit wiring structure and the secondend of at least one of the one or plurality of strips of the second unitwiring structure are mutually connected. The flexible substrate includesa gap between a side surface of the mutually connected strips and a sidesurface of the central section of the first or the second unit wiringstructure, and/or between a side surface of the mutually connectedstrips and a side surface of another strip, and is extensible in aplanar direction and a perpendicular direction of the flexible substratedue to curvatures of curves of the mutually connected strips changing.

In each of the plurality of unit wiring structures, the one or pluralityof strips may be disposed along an outer periphery of at least part ofthe central section.

The one or plurality of strips in each of the plurality of unit wiringstructures may be a plurality of strips.

The plurality of strips in each of the plurality of unit wiringstructures may curve in a clockwise or a counterclockwise manner withthe central section as a center of rotation.

An inflection point may be present at a point where the mutuallyconnected strips connect.

The plurality of unit wiring structures may further include a third unitwiring structure that is adjacent to the second unit wiring structure.The first to the third unit wiring structures may be arranged in onedirection. The second end of at least one of the plurality of strips ofthe second unit wiring structure and the second end of the at least oneof the plurality of strips of the third unit wiring structure may bemutually connected.

The plurality of unit wiring structures may further include third andfourth unit wiring structures that are mutually adjacent. The pluralityof strips in each of the first to fourth unit wiring structures may beat least three strips. The third unit wiring structure may be arrangedadjacent to the first unit wiring structure in a second direction thatintersects a first direction in which the first and second unit wiringstructures are arranged. The fourth unit wiring structure may bearranged adjacent to the second unit wiring structure in the seconddirection. Between adjacent unit wiring structures from among the firstto fourth unit wiring structures, the second end of at least one of theat least three strips of one unit wiring structure and the second end ofat least one of the at least three strips of the other unit wiringstructure may be mutually connected.

The plurality of unit wiring structures may include at least four unitwiring structures including the first and second unit wiring structures.The at least four unit wiring structures may be arranged in atwo-dimensional manner. Between adjacent unit wiring structures fromamong the at least four unit wiring structures, the second end of atleast one of the plurality of strips of one unit wiring structure andthe second end of at least one of the plurality of strips of the otherunit wiring structure may be mutually connected.

In each of the plurality of unit wiring structures, the central sectionmay be substantially circular.

Prior to extension or contraction, a center of the central section and acurve center of the one or plurality of strips may be substantiallyaligned in each of the plurality of unit wiring structures.

In each of the plurality of unit wiring structures, the plurality ofstrips may be arranged in a symmetrical manner with respect to a centerof the central section.

In each of the plurality of unit wiring structures, a curve centralangle of the one or plurality of strips may be 60 degrees or greater.

In each of the plurality of unit wiring structures, a curve centralangle of the one or plurality of strips may be 360 degrees or greater.

In each of the plurality of unit wiring structures, the one or pluralityof strips may be provided wound around the central section two or moretimes.

The flexible substrate may further comprise one or a plurality ofelectronic elements each disposed on the central section of acorresponding one of the plurality of unit wiring structures.

The flexible substrate of the present disclosure is not limited to thecategory of the field of typical electronic devices and is able to beused also in the field of wearable devices, the health care field, themedical field, and the nursing field. For example, in an electronicdevice in which extension/contraction or flexible deformation thatfollows the movement of a human body or the like is required such as awearable device, the flexible substrate of the present disclosure can beused as a wiring substrate that connects circuit modules and exhibits ahigh degree of elasticity.

What is claimed is:
 1. A flexible substrate comprising: a plurality of unit wiring structures; and a plurality of electronic elements each disposed on a central section of a corresponding one of the plurality of unit wiring structures, wherein each of the plurality of unit wiring structures includes: the central section; and at least four curved strips that are disposed at an outer side of the central section, each of the curved strips having a first end connected to the central section, the central section includes: an insulation layer; an interlayer connection via that passes through the insulation layer; a first wiring connected to the interlayer connection via; and a second wiring electrically connected to the first wiring by way of the interlayer connection via, the first wiring, the insulation layer and the second wiring are disposed in this order, two of the at least four curved strips extending in a first direction are connected to the first wiring, other two of the at least four curved strips extending in a second direction are connected to the second wiring, the second wiring has a first part and a second part separated from the first part, and each of the first part and the second part is electrically connected to the electronic element.
 2. The flexible substrate according to claim 1, wherein each of the at least four curved strips included in each of the plurality of unit wiring structures has a second end, the plurality of the unit wiring structures includes: a first unit wiring structure; a second unit wiring structure; a third unit wiring structure; a fourth unit wiring structure; and a fifth unit wiring structure, the second unit wiring structure and the third unit wiring structure are arranged adjacent to the first unit wiring structure in the first direction, the fourth unit wiring structure and the fifth unit wiring structure are arranged adjacent to the first unit wiring structure in the second direction that intersects the first direction, and each of the second ends of the at least four curved strips in the first unit wiring structure is connected to: the second end of one of the at least four curved strips in the second unit wiring structure; the second end of one of the at least four curved strips in the third unit wiring structure; the second end of one of the at least four curved strips in the fourth unit wiring structure; and the second end of one of the at least four curved strips in the fifth unit wiring structure, respectively.
 3. The flexible substrate according to claim 2, wherein the first direction is a row direction, and the second direction is a column direction.
 4. The flexible substrate according to claim 3, further comprising: a plurality of electronic elements each disposed on the central section of a corresponding one of the plurality of unit wiring structures; a plurality of row driver elements for driving the electronic elements arranged in the row direction; a plurality of column driver elements for driving the electronic elements arranged in the column direction; and a control element electrically connected to the row driver elements and the column driver elements.
 5. The flexible substrate according to claim 4, wherein the control element sends a control signal to the row driver elements through the first wiring and to the column driver elements through the second wiring, and luminance of one of the electronic elements is controlled by using a combination of at least one of the row driver elements and at least one of the column driver elements.
 6. The flexible substrate according to claim 4, wherein the electronic elements are LED elements.
 7. The flexible substrate according to claim 1, wherein the first part is connected to a cathode of one of the electronic element, and the second part is connected to an anode of the one of the electronic element.
 8. The flexible substrate according to claim 1, wherein the at least four curved strips in each of the plurality of unit wiring structures curve in a clockwise or a counterclockwise manner with the central section as a center of rotation.
 9. The flexible substrate according to claim 7, wherein the electronic elements are LED elements.
 10. The flexible substrate according to claim 1, wherein the plurality of unit wiring structures are covered with a flexible member.
 11. The flexible substrate according to claim 10, wherein the flexible member includes an elastomer.
 12. A flexible substrate comprising: a plurality of unit wiring structures, a plurality of electronic elements each disposed on a central section of a corresponding one of the plurality of unit wiring structures; a plurality of row driver elements for driving the electronic elements arranged in a row direction; a plurality of column driver elements for driving the electronic elements arranged in a column direction; and a control element electrically connected to the row driver elements and the column driver elements, wherein each of the plurality of unit wiring structures includes: the central section; and at least four curved strips that are disposed at an outer side of the central section, each of the curved strips having a first end connected to the central section, the central section includes: an insulation layer; an interlayer connection via that passes through the insulation layer; a first wiring connected to the interlayer connection via; and a second wiring electrically connected to the first wiring by way of the interlayer connection via, the first wiring, the insulation layer and the second wiring are disposed in this order, two of the at least four curved strips extending in the row direction are connected to the first wiring, other two of the at least four curved strips extending in the column direction are connected to the second wiring, each of the at least four curved strips included in each of the plurality of unit wiring structures has a second end, the plurality of the unit wiring structures includes: a first unit wiring structure; a second unit wiring structure; a third unit wiring structure; a fourth unit wiring structure; and a fifth unit wiring structure, the second unit wiring structure and the third unit wiring structure are arranged adjacent to the first unit wiring structure in the row direction, the fourth unit wiring structure and the fifth unit wiring structure are arranged adjacent to the first unit wiring structure in the column direction that intersects the row direction, and each of the second ends of the at least four curved strips in the first unit wiring structure is connected to: the second end of one of the at least four curved strips in the second unit wiring structure; the second end of one of the at least four curved strips in the third unit wiring structure; the second end of one of the at least four curved strips in the fourth unit wiring structure; and the second end of one of the at least four curved strips in the fifth unit wiring structure, respectively. 